Vertical gate separation

ABSTRACT

Methods of selectively etching tungsten from the surface of a patterned substrate are described. The methods electrically separate vertically arranged tungsten slabs from one another as needed. The vertically arranged tungsten slabs may form the walls of a trench during manufacture of a vertical flash memory cell. The tungsten etch may selectively remove tungsten relative to films such as silicon, polysilicon, silicon oxide, aluminum oxide, titanium nitride and silicon nitride. The methods include exposing electrically-shorted tungsten slabs to remotely-excited fluorine formed in a remote plasma region. Process parameters are provided which result in uniform tungsten recess within the trench. A low electron temperature is maintained in the substrate processing region to achieve high etch selectivity and uniform removal throughout the trench.

FIELD

The subject matter herein relates to electrical separation of gates in avertical memory structure.

BACKGROUND

Integrated circuits are made possible by processes which produceintricately patterned material layers on substrate surfaces. Producingpatterned material on a substrate requires controlled methods forremoval of exposed material. Chemical etching is used for a variety ofpurposes including transferring a pattern in photoresist into underlyinglayers, thinning layers or thinning lateral dimensions of featuresalready present on the surface. Often it is desirable to have an etchprocess which etches one material faster than another helping e,g. apattern transfer process proceed. Such an etch process is said to beselective of the first material. As a result of the diversity ofmaterials, circuits and processes, etch processes have been developedthat selectively remove one or more of a broad range of materials.

Dry etch processes are increasingly desirable for selectively removingmaterial from semiconductor substrates. The desirability stems from theability to gently remove material from miniature structures with minimalphysical disturbance. Dry etch processes also allow the etch rate to beabruptly stopped by removing the gas phase reagents. Some dry-etchprocesses involve the exposure of a substrate to remote plasmaby-products formed from one or more precursors. For example, remoteplasma generation of nitrogen trifluoride in combination with ionsuppression techniques enables silicon to be and selectively removedfrom a patterned substrate when the plasma effluents are flowed into thesubstrate processing region.

Methods are needed to broaden the utility of selective dry etchprocesses.

SUMMARY

Methods of selectively etching tungsten from the surface of a patternedsubstrate are described. The methods electrically separate verticallyarranged tungsten slabs from one another as needed. The verticallyarranged tungsten slabs may form the walls of a trench duringmanufacture of a vertical flash memory cell. The tungsten etch mayselectively remove tungsten relative to films such as silicon,polysilicon, silicon oxide, aluminum oxide, titanium nitride and siliconnitride. The methods include exposing electrically-shorted tungstenslabs to remotely-excited fluorine formed in a remote plasma region.Process parameters are provided which result in uniform tungsten recesswithin the trench. A low electron temperature is maintained in thesubstrate processing region to achieve high etch selectivity and uniformremoval throughout the trench.

Embodiments include methods of etching a patterned substrate. Themethods include placing the patterned substrate in a substrateprocessing region of a substrate processing chamber. The patternedsubstrate includes electrically-shorted tungsten slabs arranged in atleast one of two adjacent vertical columns. A trench is formed betweenthe two adjacent vertical columns. The methods further include flowing afluorine-containing precursor into a remote plasma region within thesubstrate processing chamber and exciting the fluorine-containingprecursor in a remote plasma in the remote plasma region to produceplasma effluents. The remote plasma region is fluidly coupled with thesubstrate processing region through a showerhead and the remote plasmais capacitively-coupled. The methods further include flowing the plasmaeffluents into the substrate processing region through the showerheadand etching the electrically-shorted tungsten slabs.

The remote plasma may be capacitively-coupled with a remote plasma powerof between 100 watts and 500 watts. An electron temperature in thesubstrate processing region while selectively etching theelectrically-shorted tungsten slabs may be below 0.5 eV. Etching theelectrically-shorted tungsten slabs electrically may isolate theelectrically-shorted tungsten slabs from one another to formelectrically-isolated tungsten slabs, The fluorine-containing precursormay include at least one of atomic fluorine, diatomic fluorine, brominetrifluoride, chlorine trifluoride, nitrogen trifluoride, hydrogenfluoride, fluorinated hydrocarbons, sulfur hexafluoride and xenondifluoride. A depth-to-width aspect ratio of the trench may be at leastten. At least one of the two adjacent vertical columns include at leastthirty tungsten slabs. A depth of the trench may be greater than onemicron. A temperature of the patterned substrate may be maintained atbetween 50° C. and about 80° C. during etching the electrically-shortedtungsten slabs. The electrically-shorted tungsten slabs may consist oftungsten and a barrier layer. A pressure within the remote plasma regionmay be between 5 Torr and 12 Ton during etching the electrically-shortedtungsten slabs.

Embodiments include methods of etching a patterned substrate. Themethods include placing the patterned substrate in a substrateprocessing region of a substrate processing chamber. The patternedsubstrate includes electrically-shorted conducting slabs arranged in avertical column. A trench is disposed between the vertical column and anadjacent vertical column. The methods further include gas-phase etchingthe electrically-shorted conducting slabs. The operation of gas-phaseetching electrically separates the electrically-shorted conducting slabsto form electrically-isolated conducting slabs. The methods furtherinclude recessing the electrically-isolated conducting slabs beyond anextent of insulating material between each adjacent pair of theelectrically-isolated conducting slabs by a recessed amount.

A standard deviation of a statistical distribution of the recessedamounts of all the electrically-isolated conducting slabs may be lessthan 0.5 nm prior to the operation of gas-phase etching theelectrically-shorted conducting slabs and/or may be less than 0.5 nmafter the operation of gas-phase etching the electrically-shortedconducting slabs.

Embodiments include methods of etching a patterned substrate. Themethods include placing the patterned substrate in a substrateprocessing region of a substrate processing chamber. The patternedsubstrate comprises electrically-shorted tungsten slabs arranged in atleast one of two adjacent vertical columns. A trench is disposed betweenthe two adjacent vertical columns. The methods further include flowing aradical-fluorine precursor into the substrate processing region. Themethods further include selectively etching the electrically-shortedtungsten slabs. Selectively etching the electrically-shorted tungstenslabs electrically isolates each of the electrically-shorted tungstenslabs from one another to form electrically-isolated tungsten slabs.

Additional embodiments and features are set forth in part in thedescription that follows, and in part will become apparent to thoseskilled in the art upon examination of the specification or may belearned by the practice of the disclosed embodiments. The features andadvantages of the disclosed embodiments may be realized and attained bymeans of the instrumentalities, combinations, and methods described inthe specification.

DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the embodimentsmay be realized by reference to the remaining portions of thespecification and the drawings.

FIGS. 1A and 1B are cross-sectional views of a patterned substrateduring an tungsten etch process according to embodiments.

FIG. 2 is a flow chart of a tungsten etch process according toembodiments.

FIG. 3A shows a schematic cross-sectional view of a substrate processingchamber according to embodiments.

FIG. 3B shows a schematic cross-sectional view of a portion of asubstrate processing chamber according to embodiments.

FIG. 3C shows a bottom view of a showerhead according to embodiments.

FIG. 4 shows a top view of an exemplary substrate processing systemaccording to embodiments.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

DETAILED DESCRIPTION

Methods of selectively etching tungsten from the surface of a patternedsubstrate are described. The methods electrically separate verticallyarranged tungsten slabs from one another as needed. The verticallyarranged tungsten slabs may form the walls of a trench duringmanufacture of a vertical flash memory cell. The tungsten etch mayselectively remove tungsten relative to films such as silicon,polysilicon, silicon oxide, aluminum oxide, titanium nitride and siliconnitride. The methods include exposing electrically-shorted tungstenslabs to remotely-excited fluorine formed in a remote plasma region.Process parameters are provided which result in uniform tungsten recesswithin the trench. A low electron temperature is maintained in thesubstrate processing region to achieve high etch selectivity and uniformremoval throughout the trench.

Vertical flash memory may be referred to as 3-D flash memory andincludes a plurality of electrically-isolated conducting slabs arrangedin at least one of two adjacent vertical columns. Tungsten is currentlyin widespread use for the conducting slab material. The number of slabsis increasing to increase the amount of storage per integrated circuit(IC). As the number of slabs is increased, the depth of a trench betweentwo adjacent vertical columns is also increased. Maintaining a uniformremoval from the top of the trench down to the bottom of the trench isdesirable fora tungsten etch operation to recess and separate thetungsten slabs. The methods described herein provide benefit whicharises from a more uniform reduction of tungsten film thickness up anddown the sides of the trench using a single operation rather than asequence of operations which possess offsetting inhomogeneous etchrates. The benefit includes a larger average amount of tungstenremaining after electrical separation which improves the electricalperformance of the memory. The methods provide benefit from decreasedprocess complexity in that no non-uniform compensating operations arenecessary in embodiments. The methods may also avoid reliance on the useof a local plasma or a bias plasma power. No local plasma (e.g. no biaspower) is applied to the substrate processing region during all etchingoperations described herei). The etch selectivity is desirably increasedby avoiding local plasma excitation (applying plasma power directly tothe substrate processing region).

To better understand and appreciate the embodiments described herein,reference is now made to FIGS. 1A and 1B which are cross-sectional viewsof a 3-D flash memory cell during a method 201 (see FIG. 2) of formingthe 3-D flash memory cells according to embodiments. In one example, aflash memory cell on patterned substrate 101 comprises alternativelystacked silicon oxide 105 and tungsten 110-1 in two adjacent columns.Tungsten 110-1 has recently been deposited into the stack, replacingsacrificial silicon nitride at the levels shown in FIG. 1A. FIG. 1Ashows only five levels of tungsten to allow a more detailed discussionof the tungsten etch process 201. There may be more than thirty, morethan fifty, more than seventy or more than ninety tungsten levelsaccording to embodiments.

Tungsten deposited outside the stack shorts the tungsten levels togetheras shown in FIG. 1A. Tungsten 110 may consist essentially of or consistof tungsten in embodiments. Tungsten 110 may consist of tungsten and abarrier layer in embodiments. The trench in which tungsten has beendeposited may be called a “slit trench” between the two adjacent columnsto indicate that this trench has a much larger length-to-width aspectratio (longer into the page) than the memory hole also shown in FIG. 1A.The depth-to-width aspect ratio (depth divided by width) of the slittrench may be greater than ten, fifteen or twenty according toembodiments. The depth is measured vertically and the width is measuredhorizontally in the plane of FIG. 1A. The sides of the memory hole arelined with a conformal ONO layer. The ONO layer includes a silicon oxidelayer 115 (often referred to as IPD or interpoly dielectric), a siliconnitride layer 120 (which serves as the charge trap layer) and a siliconoxide layer 125 (the gate dielectric) “Top” and “Up” will be used hereinto describe portions/directions perpendicularly distal from thesubstrate plane and further away from the center of mass of thesubstrate in the perpendicular direction. “Vertical” will be used todescribe items aligned in the “Up” direction towards the “Top”. Othersimilar terms may be used whose meanings will now be clear. The verticalmemory hole may be circular as viewed from above.

The conformal ONO layer may be used as an etch stop for the selectivegas-phase tungsten etch and the structure of the conformal ONO layerwill now be described. The tungsten barrier layer may also be used as anetch stop in embodiments. Silicon oxide layer 115 may be in contact withsilicon nitride layer 120, which may be in contact with silicon oxidelayer 125 in embodiments. Silicon oxide layer 115 may contact stackedsilicon oxide layers 105 and stacked tungsten layers 110 whereas siliconoxide layer 125 may contact silicon 101 (epitaxially grown) or apolysilicon layer in embodiments. Silicon oxide layer 115 may have athickness less than or about 8 nm or less than 6 nm in embodiments.Silicon oxide layer 115 may comprise or consist of silicon and oxygen inembodiments. Silicon nitride 120 may have a thickness less than or about8 nm or less than 6 nm in embodiments. Silicon nitride layer 120 maycomprise or consist of silicon and nitrogen in embodiments. Siliconoxide layer 125 may have a thickness less than or about 8 nm or lessthan 6 nm in embodiments. Silicon oxide layer 125 may comprise orconsist of silicon and oxygen in embodiments. The constrained geometriesand thinness of the layers result in damage to the memory cell whenliquid etchants are used, further motivating the gas-phase etchingmethods presented herein. Liquid etchants cannot be as completelyremoved and continue to etch after etchants are supposedly removed inembodiments. Liquid etchants may ultimately form and/or penetratethrough pinholes and damage devices after manufacturing is complete.

Patterned substrate 101 as shown in FIG. 1A is delivered into asubstrate processing chamber. Patterned substrate 101 is transferredinto a substrate processing region within a substrate processing chamber(operation 210) to initiate method 201 of forming a flash memoty cell. Aflow of nitrogen trifluoride is then introduced into a remote plasmaregion where the nitrogen trifluoride is excited in a remote plasmastruck within the remote plasma region in operation 220. The remoteplasma region may be a remote plasma system (RPS) located outside thesubstrate processing chamber and/or a chamber plasma region locatedinside the substrate processing region. The remote plasma region isseparated from the substrate processing region by an aperture or ashowerhead. In general, a fluorine-containing precursor may be flowedinto the chamber plasma region and the fluorine-containing precursorcomprises at least one precursor selected from the group consisting ofatomic fluorine, diatomic fluorine, bromine trifluoride, chlorinetrifluoride, nitrogen trifluoride, hydrogen fluoride, fluorinatedhydrocarbons, sulfur hexafluoride and xenon difluoride. Also inoperation 220, plasma effluents formed in the remote plasma region areflowed through the aperture or showerhead into the substrate processingregion housing patterned substrate 101.

According to embodiments, the plasma effluents may pass through ashowerhead and/or ion suppressor to reduce the electron temperature (toreduce the ion concentration) in the substrate processing region.Reduced electron temperatures as described subsequently herein have beenfound to increase the etch selectivity of tungsten compared to otherexposed materials (e.g. silicon oxide or silicon nitride). Reducedelectron temperatures apply to all tungsten etch operations describedherein using either chamber plasma regions or remote plasma systems orthe combination of the two in the integrated process described below.The low electron temperatures are described later in the specification(e.g. <0.5 eV). Operation 230 (and all etches described herein) may bereferred to as a gas-phase etch to distinguish from liquid etchprocesses. In operation 230, tungsten is selectively etched back toelectrically separate tungsten layers 110-1 from one another to formseparate tungsten layers 110-2. The reactive chemical species areremoved from the substrate processing region and the substrate isremoved from the substrate processing region in operation 240.

For the purposes of dimensions and other characterizations describedherein, tungsten and tungsten slabs will be understood to include theirbarrier layers or other conformal layers useful for forming or using thetungsten or tungsten slabs. Exemplary tungsten barrier layers mayinclude titanium, titanium nitride, tantalum or tantalum nitride inembodiments. The barrier layer may also provide etch stop functionalityin the etch processes described herein.

In addition to the fluorine-containing precursor flowing into the remoteplasma region, some additional precursors may be helpful to make theetch operation 230 selective of the tungsten slabs 110-1. Anoxygen-containing precursor, e.g. molecular oxygen, may be flowed intothe remote plasma region in combination or to combine with thefluorine-containing precursor in embodiments. Alternatively, or incombination, a hydrogen-containing precursor, e.g. molecular hydrogen,may be flowed into the remote plasma region in combination or to combinewith the fluorine-containing precursor in embodiments. According toembodiments, the plasma effluents may pass through a showerhead and/orion suppressor to reduce the electron temperature (to reduce the ionconcentration) in the substrate processing region. Reduced electrontemperatures as described subsequently herein have been found toincrease the etch selectivity of tungsten in tungsten slabs 110 comparedto other exposed materials.

Operation 220 may include applying energy to the fluorine-containingprecursor while in the chamber plasma region to generate the plasmaeffluents. As would be appreciated by one of ordinary skill in the art,the plasma may include a number of charged and neutral species includingradicals and ions. The plasma may be generated using known techniques(e.g., radio frequency excitations, capacitively-coupled power orinductively coupled power). In an embodiment, the energy is appliedusing a capacitively-coupled plasma unit. The remote plasma power may bebetween 25 watts and 2000 watts, between 50 watts and 1000 watts orbetween 100 watts and 500 watts according to embodiments. Thecapacitively-coupled plasma unit may be disposed remote from a substrateprocessing region of the processing chamber. For example, thecapacitively-coupled plasma unit and the plasma generation region may beseparated from the substrate processing region by a showerhead. Allprocess parameters (e.g. power above, temperature and pressure below)apply to all remote plasma embodiments herein unless otherwiseindicated.

In operations described herein, the fluorine-containing precursor (e.g.NF₃) is supplied at a flow rate of between 5 sccm and 500 sccm, between10 sccm and 300 sccm, between 25 sccm and 200 sccm, between 50 sccm and150 sccm or between 75 sccm and 125 sccm. The temperature of thepatterned substrate may be between −20° C. and 200° C. during tungstenselective etches described herein. The patterned substrate temperaturemay also be maintained at between 30° C. and 110° C., between 50° C. and80° C. or between 55° C. and 75° C. during all the gas-phase etchingprocesses according to embodiments. These process parameters apply toall the embodiments described herein. The pressure within the substrateprocessing region is below 50 Torr, below 30 Torr, below 20 Torr, below15. The pressure may be above 0.5 Torr, above 1.0 Torr, above 1.5 Torror above 3 Torr in embodiments. In a preferred embodiment, the pressurewhile etching may be between 5 Torr and 12 Torr. However, any of theupper limits on temperature or pressure may be combined with lowerlimits to form additional embodiments.

An advantage of the processes described herein lies in the conformalrate of removal of material from the substrate. The methods do not relyon a high bias power (or any bias power in embodiments) to accelerateetchants towards the substrate, which reduces the tendency of the etchprocesses to remove material on the tops and bottom of trenches beforematerial on the sidewalk can be removed. As used herein, a conformaletch process refers to a generally uniform removal rate of material froma patterned surface regardless of the shape of the surface. The surfaceof the layer before and after the etch process are generally parallel. Aperson having ordinary skill in the art will recognize that the etchprocess likely cannot be 100% conformal and thus the term “generally”allows for acceptable tolerances.

The tungsten slabs 110-2 of the 3-D flash memory device formed usingetch process 201 may each end up recessed within 1 urn of the averagerecess of the electrically-isolated tungsten slabs in embodiments. Thestandard deviation of the lengths of each tungsten slab 110-2 (measuredleft-right in FIG. 1B) may be under 0.5 nm before and/or after operation230 according to embodiments. Operation 230 electrically isolates theelectrically-shorted tungsten slabs 110-1 from one another to formelectrically-isolated tungsten slabs 110-2 having more homogeneousrecesses compared to previously-developed processes.Electrically-isolated tungsten slabs 110-2 may each beelectrically-isolated from every other of the electrically-isolatedtungsten slabs 110-2 according to embodiments.

In each remote plasma described herein, the flows of the precursors intothe remote plasma region may further include one or more relativelyinert gases such as He, N₂, Ar. The inert gas can be used to improveplasma stability, ease plasma initiation, and improve processuniformity. Argon is helpful, as an additive, to promote the formationof a stable plasma. Process uniformity is generally increased whenhelium is included. These additives are present in embodimentsthroughout this specification. Flow rates and ratios of the differentgases may be used to control etch rates and etch selectivity.

In embodiments, an ion suppressor (which may be the showerhead) may beused to provide radical and/or neutral species for gas-phase etching.The ion suppressor may also be referred to as an ion suppressionelement. In embodiments, for example, the ion suppressor is used tofilter etching plasma effluents en route from the remote plasma regionto the substrate processing region. The ion suppressor may be used toprovide a reactive gas having a higher concentration of radicals thanions. Plasma effluents pass through the ion suppressor disposed betweenthe remote plasma region and the substrate processing region. The ionsuppressor functions to dramatically reduce or substantially eliminateionic species traveling from the plasma generation region to thesubstrate. The ion suppressors described herein are simply one way toachieve a low electron temperature in the substrate processing regionduring the gas-phase etch processes described herein.

In embodiments, an electron beam is passed through the substrateprocessing region in a plane parallel to the substrate to reduce theelectron temperature of the plasma effluents. A simpler showerhead maybe used if an electron beam is applied in this manner. The electron beammay be passed as a laminar sheet disposed above the substrate inembodiments. The electron beam provides a source of neutralizingnegative charge and provides a more active means for reducing the flowof positively charged ions towards the substrate and increasing the etchselectivity in embodiments. The flow of plasma effluents and variousparameters governing the operation of the electron beam may be adjustedto lower the elec ron temperature measured in the substrate processingregion.

The electron temperature may be measured using a Langmuir probe in thesubstrate processing region during excitation of a plasma in the remoteplasma. The electron temperature may be less than 0.5 eV, less than 0.45eV, less than 0.4 eV, or less than 0.35 eV. These extremely low valuesfor the electron temperature are enabled by the presence of the electronbeam, showerhead and/or the ion suppressor. Uncharged neutral andradical species may pass through the electron beam and/or the openingsin the ion suppressor to react at the substrate. Such a process usingradicals and other neutral species can reduce plasma damage compared toconventional plasma etch processes that include sputtering andbombardment. Embodiments are also advantageous over conventional wetetch processes where surface tension of liquids can cause bending andpeeling of small features.

The substrate processing region may be described herein as “plasma-free”during the etch processes described herein. “Plasma-free” does notnecessarily mean the region is devoid of plasma. Ionized species andfree electrons created within the plasma region may travel through pores(apertures) in the partition (showerhead) at exceedingly smallconcentrations. The borders of the plasma in the chamber plasma regionare hard to define and may encroach upon the substrate processing regionthrough the apertures in the showerhead. Furthermore, a low intensityplasma may be created in the substrate processing region withouteliminating desirable features of the etch processes described herein.All causes for a plasma having much lower intensity ion density than thechamber plasma region during the creation of the excited plasmaeffluents do not deviate from the scope of “plasma-free” as used herein.

The etch selectivities during the tungsten etches described herein(tungsten:silicon oxide or tungsten:silicon nitride ortungsten:polysilicon and tungsten:titanium nitride (or another barriermaterial listed herein)) may be greater than or about 50:1, greater thanor about 100:1, greater than or about 150:1 or greater than or about250:1 according to embodiments.

FIG. 3A shows a cross-sectional view of an exemplary substrateprocessing chamber 1001 with a partitioned plasma generation regionwithin the processing chamber. During film etching, a process gas may beflowed into chamber plasma region 1015 through a gas inlet assembly1005. A remote plasma system (RPS) 1002 may optionally be included inthe system, and may process a first as which then travels through gasinlet assembly 1005. The process gas may be excited within RPS 1002prior to entering chamber plasma region 1015. Accordingly, thefluorine-containing precursor as discussed above, for example, may passthrough RPS 1002 or bypass the RPS unit in embodiments.

A cooling plate 1003, faceplate 1017, ion suppressor 1023, showerhead1025, and a substrate support 1065 (also known as a pedestal), having asubstrate 1055 disposed thereon, are shown and may each be includedaccording to embodiments. Pedestal 1065 may have a heat exchange channelthrough which a heat exchange fluid flows to control the temperature ofthe substrate. This configuration may allow the substrate 1055temperature to be cooled or heated to maintain relatively lowtemperatures, such as between −20° C. to 200° C. Pedestal 1065 may alsobe resistively heated to relatively high temperatures, such as between100° C. and 1100° C., using an embedded heater element.

Exemplary configurations may nclude having the gas inlet assembly 1005open into a gas supply region 1058 partitioned from the chamber plasmaregion 1015 by faceplate 1017 so that the gases/species flow through theholes in the faceplate 1017 into the chamber plasma region 1015.Structural and operational features may be selected to preventsignificant backflow of plasma from the chamber plasma region 1015 backinto the supply region 1058, gas inlet assembly 1005, and fluid supplysystem 1010. The structural features may include the selection ofdimensions and cross-sectional geometries of the apertures in faceplate1017 to deactivate back-streaming plasma. The operational features mayinclude maintaining a pressure difference between the gas supply region1058 and chamber plasma region 1015 that maintains a unidirectional flowof plasma through the showerhead 1025. The faceplate 1017, or aconductive top portion of the chamber, and showerhead 1025 are shownwith an insulating ring 1020 located between the features, which allowsan AC potential to be applied to the faceplate 1017 relative toshowerhead 1025 and/or ion suppressor 1023. The insulating ring 1020 maybe positioned between the faceplate 1017 and the showerhead 1025 and/orion suppressor 1023 enabling a capacitively coupled plasma (CCP) to beformed in the first plasma region.

The plurality of holes in the ion suppressor 1023 may be configured tocontrol the passage of the activated gas, i.e., the ionic, radical,and/or neutral species, through the ion suppressor 1023. For example,the aspect ratio of the holes, or the hole diameter to length, and/orthe geometry of the holes may be controlled so that the flow ofionicaily-charged species in the activated gas passing through the ionsuppressor 1023 is reduced. The holes in the ion suppressor 1023 mayinclude a tapered portion that faces chamber plasma region 1015, and acylindrical portion that faces the showerhead 1025. The cylindricalportion may be shaped and dimensioned to control the flow of ionicspecies passing to the showerhead 1025. An adjustable electrical biasmay also be applied to the ion suppressor 1023 as an additional means tocontrol the flow of ionic species through the suppressor. The ionsuppression element 1023 may function to reduce or eliminate the amountof ionically charged species traveling from the plasma generation regionto the substrate. Uncharged neutral and radical species may still passthrough the openings in the ion suppressor to react with the substrate.

Plasma power can be of a variety of frequencies or a combination ofmultiple frequencies. In the exemplary processing system the plasma maybe provided by RE power delivered to faceplate 1017 relative to ionsuppressor 1023 and/or showerhead 1025. The RE frequency applied in theexemplary processing system may be low RF frequencies less than about200 kHz, high RF frequencies between about 10 MHz and about 15 MHz, ormicrowave frequencies greater than or about 1 GHz in embodiments, Theplasma power may be capacitively-coupled (CCP) or inductively-coupled(ICP) into the remote plasma region.

A precursor, for example a fluorine-containing precursor, may be flowedinto substrate processing region 1033 by embodiments of the showerheaddescribed herein. Excited species derived from the process gas inchamber plasma region 1015 may travel through apertures in the ionsuppressor 1023, and/or showerhead 1025 and react with an additionalprecursor flowing into substrate processing region 1033 from a separateportion of the showerhead. Alternatively, if all precursor species arebeing excited in chamber plasma region 1015, no additional precursorsmay be flowed through the separate portion of the showerhead. Little orno plasma may be present in substrate processing region 1033 during theremote plasma etch process. Excited derivatives of the precursors maycombine in the region above the substrate and/or on the substrate toetch structures or remove species from the substrate.

The processing gases may be excited in chamber plasma region 1015 andmay be passed through the showerhead 1025 to substrate processing region1033 in the excited state. While a plasma may be generated in substrateprocessing region 1033, a plasma may alternatively not be generated inthe processing region. In one example, the only excitation of theprocessing gas or precursors may be from exciting the processing gasesin chamber plasma region 1015 to react with one another in substrateprocessing region 1033. As previously discussed, this may be to protectthe structures patterned on substrate 1055.

FIG. 3B shows a detailed view of the features affecting the processinggas distribution through faceplate 1017. The gas distribution assembliessuch as showerhead 1025 for use in the processing chamber section 1001may be referred to as dual channel showerheads (DCSH) and areadditionally detailed in the eMbodiments described in FIG. 3A as well asFIG. 3C herein. The dual channel showerhead may provide for etchingprocesses that allow for separation of etchants outside of theprocessing region 1033 to provide limited interaction with chambercomponents and each other prior to being delivered into the processingregion.

The showerhead 1025 may comprise an upper plate 1014 and a tower plate1016. The plates may be coupled with one another to define a volume 1018between the plates. The coupling of the plates may be so as to providefirst fluid channels 1019 through the upper and lower plates, and secondfluid channels 1021 through the tower plate 1016. The formed channelsmay be configured to provide fluid access from the volume 1018 throughthe lower plate 1016 via second fluid channels 1021 alone, and the firstfluid channels 1019 may be fluidly isolated from the volume 1018 betweenthe plates and the second fluid channels 1021. The volume 1018 may befluidly accessible through a side of the gas distribution assembly 1025.Although the exemplary system of FIGS. 3A-3C includes a dual-channelshowerhead, it is understood that alternative distribution assembliesmay be utilized that maintain first and second precursors fluidlyisolated prior to substrate processing region 1033. For example, aperforated plate and tubes underneath the plate may be utilized,although other configurations may operate with reduced efficiency or notprovide as uniform processing as the dual-channel showerhead asdescribed.

In the embodiment shown, showerhead 1025 may distribute via first fluidchannels 1019 process gases which contain plasma effluents uponexcitation by a plasma in chamber plasma region 1015. In embodiments,the process gas introduced into RPS 1002 andlor chamber plasma region1015 may contain fluorine, e.g., NF₃. The process gas may also include acarrier gas such as helium, argon, nitrogen (N₂), etc. Plasma effluentsmay include ionized or neutral derivatives of the process gas and mayalso be referred to herein as a radical-fluorine precursor referring tothe atomic constituent of the process gas introduced.

FIG. 3C is a bottom view of a showerhead 1025 for use with a processingchamber in embodiments. Showerhead 1025 corresponds with the showerheadshown in FIG. 3A. Through-holes 1031, which show a view of first fluidchannels 1019, may have a plurality of shapes and configurations tocontrol and affect the flow of precursors through the showerhead 1025.Small holes 1027, which show a view of second fluid channels 1021, maybe distributed substantially evenly over the surface of the showerhead,even amongst the through-holes 1031, which may help to provide more evenmixing of the precursors as they exit the showerhead than otherconfigurations.

The chamber plasma region 1015 or a region in an RPS may be referred toas a remote plasma region. In embodiments, the radical precursor, e.g.,a radical-fluorine precursor, is created in the remote plasma region andtravels into the substrate processing region where it may or may notcombine with additional precursors. In embodiments, the additionalprecursors are excited only by the radical-fluorine precursor. Plasmapower may essentially be applied only to the remote plasma region inembodiments to ensure that the radical-fluorine precursor provides thedominant excitation.

Combined flow rates of precursors into the chamber may account for 0.05%to about 20% by volume of the overall gas mixture; the remainder beingcarrier gases. The fluorine-containing precursor may be flowed into theremote plasma region, but the plasma effluents ay have the samevolumetric flow ratio in embodiments. In the case of thefluorine-containing precursor, a purge or carrier gas may be flowedinitially into the remote plasma region before the fluorine-containinggas to stabilize the pressure within the remote plasma region. Substrateprocessing region 1033 can be maintained at a variety of pressuresduring the flow of precursors, any carrier gases, and plasma effluentsinto substrate processing region 1033.

Embodiments of the dry etch systems may be incorporated into largerfabrication systems for producing integrated circuit chips. FIG. 4 showsone such processing system (mainframe) 1101 of deposition, etching,baking, and curing chambers in embodiments. In the figure, a pair offront opening unified pods (load lock chambers 1102) supply substratesof a variety of sizes that are received by robotic arms 1104 and placedinto a low pressure holding area 1106 before being placed into one ofthe substrate processing chambers 1108 a-f. A second robotic arm 1110may be used to transport the substrate wafers from the holding area 1106to the substrate processing chambers 1108 a-f and back. Each substrateprocessing chamber 1108 a-f, can be outfitted to perform a number ofsubstrate processing operations including the dry etch processesdescribed herein in addition to cyclical layer deposition (CLD), atomiclayer deposition (ALD), chemical vapor deposition (CVD), physical vapordeposition (PVD), etch, pre-clean, degas, orientation, and othersubstrate processes. The substrate processing chambers 1108 a-f may beconfigured for depositing, annealing, curing and/or etching a film onthe substrate water.

In the preceding description, for the purposes of explanation, numerousdetails have been set forth to provide an understanding of embodimentsof the subject matter described herein. It will be apparent to oneskilled in the art, however, that certain embodiments may be practicedwithout some of these details, or with additional details.

As used herein “substrate” may be a support substrate with or withoutlayers formed thereon. The patterned substrate may be an insulator or asemiconductor of a variety of doping concentrations and profiles andmay, for example, be a semiconductor substrate of the type used in themanufacture of integrated circuits. Exposed “silicon” or “polysilicon”of the patterned substrate is predominantly Si but may include minorityconcentrations of other elemental constituents such as nitrogen, oxygen,hydrogen and carbon. Exposed “silicon” or “polysilicon” may consist ofor consist essentially of silicon. Exposed “silicon nitride” of thepatterned substrate is predominantly silicon and nitrogen but mayinclude minority concentrations of other elemental constituents such asoxygen, hydrogen and carbon. “Exposed silicon nitride” may consistessentially of or consist of silicon and nitrogen. Exposed “siliconoxide” of the patterned substrate is predominantly SiO₂ but may includeminority concentrations of other elemental constituents such asnitrogen, hydrogen and carbon. In embodiments, silicon oxide filmsetched using the methods taught herein consist essentially of or consistof silicon and oxygen. Analogous definitions will he understood for“tungsten”, “titanium”, “titanium nitride”, “tantalum” and “tantalumnitride”.

The term “precursor” is used to refer to any process gas which takespart in a reaction to either remove material from or deposit materialonto a surface. “Plasma effluents” describe gas exiting from the chamberplasma region and entering the substrate processing region. Plasmaeffluents are in an “excited state” wherein at least some of the gasmolecules are in vibrationally-excited, dissociated and/or ionizedstates. A “radical precursor” is used to describe plasma effluents a gasin an excited state which is exiting a plasma which participate in areaction to either remove material from or deposit material on asurface. “Radical-fluorine” is a radical precursor which containsfluorine but may contain other elemental constituents. The phrase “inertgas” refers to any gas which does not form chemical bonds when etchingor being incorporated into a film. Exemplary inert gases include noblegases but may include other gases so long as no chemical bonds areformed when (typically) trace amounts are trapped in a film.

The term “gap” is used with no implication that the etched geometry hasa large length-to-width aspect ratio. Viewed from above the surface,gaps may appear circular, oval, polygonal, rectangular, or a variety ofother shapes. The term “gap” refers to a “trench” or a “via”. Alength-to-width aspect ratio of the via may be about 1:1, as viewed fromabove, whereas a length-to-width aspect ratio of the trench may begreater than 10:1. A trench may be in the shape of a moat around anisland of material in which case the length-to-width aspect ratio wouldbe the circumference divided by the width of the gap averaged around thecircumference. The term “via” is used to refer to a low length-to-widthaspect ratio trench which may or may not be filled with metal to form avertical electrical connection. As used herein, a conformal etch processrefers to a generally uniform removal of material on a surface in thesame shape as the surface, i.e., the surface of the etched layer and thepre-etch surface are generally parallel. A person having ordinary skillin the art will recognize that the etched interface likely cannot be100% conformal and thus the term “generally” allows for acceptabletolerances.

Having disclosed several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of thedisclosed embodiments. Additionally, a number of well-known processesand elements have not been described to avoid unnecessarily obscuringthe embodiments described herein. Accordingly, the above descriptionshould not be taken as limiting the scope of the claims.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassed.The upper and lower limits of these smaller ranges may independently beincluded or excluded in the range, and each range where either, neitheror both limits are included in the smaller ranges is also encompassedwithin the embodiments described, subject to any specifically excludedlimit in the stated range. Where the stated range includes one or bothof the limits, ranges excluding either or both of those included limitsare also included.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a process” includes aplurality of such processes and reference to “the dielectric material”includes reference to one or more dielectric materials and equivalentsthereof known to those skilled in the art, and so forth.

Also, the words “comprise,” “comprising,” “include,” “including,” and“includes” when used in this specification and in the following claimsare intended to specify the presence of stated features, integers,components, or steps, but they do not preclude the presence or additionof one or more other features, integers, components, steps, acts, orgroups.

1. A method of etching a patterned substrate, the method comprising:placing the patterned substrate in a substrate processing region of asubstrate processing chamber, wherein the patterned substrate compriseselectrically-shorted tungsten slabs arranged in at least one of twoadjacent vertical columns, wherein a trench is disposed between the twoadjacent vertical columns; flowing a fluorine-containing precursor intoa remote plasma region within the substrate processing chamber andexciting the fluorine-containing precursor in a remote plasma in theremote plasma region to produce plasma effluents, wherein the remoteplasma region is fluidly coupled with the substrate processing regionthrough a showerhead and the remote plasma is capacitively-coupled; andflowing the plasma effluents into the substrate processing regionthrough the showerhead and etching the electrically-shorted tungstenslabs, wherein an electron temperature in the substrate processingregion while selectively etching the electrically-shorted tungsten slabsis below 0.5 eV, and wherein a pressure within the remote plasma regionis between 5 Torr and 12 Torr during etching the electrically-shortedtungsten slabs.
 2. The method of claim 1 wherein the remote plasma iscapacitively-coupled with a remote plasma power of between 100 watts and500 watts.
 3. (canceled)
 4. The method of claim 1 wherein etching theelectrically-shorted tungsten slabs electrically isolates theelectrically-shorted tungsten slabs from one another to formelectrically-isolated tungsten slabs.
 5. The method of claim 1 whereinthe fluorine-containing precursor comprises at least one of atomicfluorine, diatomic fluorine, bromine trifluoride, chlorine trifluoride,nitrogen trifluoride, hydrogen fluoride, fluorinated hydrocarbons,sulfur hexafluoride and xenon difluoride.
 6. The method of claim 1wherein a depth-to-width aspect ratio of the trench is at least ten. 7.The method of claim 1 wherein the at least one of the two adjacentvertical columns comprise at least thirty tungsten slabs.
 8. The methodof claim 1 wherein a depth of the trench is greater than one micron. 9.The method of claim 1 wherein a temperature of the patterned substrateis maintained at between 50° C. and about 80° C. during etching theelectrically-shorted tungsten slabs.
 10. The method of claim 1 whereinthe electrically-shorted tungsten slabs consist of tungsten and abarrier layer.
 11. (canceled)
 12. A method of etching a patternedsubstrate, the method comprising: placing the patterned substrate in asubstrate processing region of a substrate processing chamber, whereinthe patterned substrate comprises electrically-shorted conducting slabsarranged in a vertical column, wherein a trench is disposed between thevertical column and an adjacent vertical column; generating a plasma ina remote plasma region of the substrate processing chamber, wherein theremote plasma region is physically separated from the substrateprocessing region by at least one chamber component, and wherein theplasma produces plasma effluents; reducing the electron temperature ofthe plasma effluents by passing the plasma effluents through an electronbeam generated in the substrate processing region of the chamber,wherein the substrate processing region is maintained plasma free;gas-phase etching the electrically-shorted conducting slabs, wherein theoperation of gas-phase etching electrically separates theelectrically-shorted conducting slabs to form electrically-isolatedconducting slabs; and recessing the electrically-isolated conductingslabs beyond an extent of insulating material between each adjacent pairof the electrically-isolated conducting slabs by a recessed amount. 13.The method of claim 12 wherein each conducting slab is characterized bya length parallel to the substrate, and wherein the length of each slabis within 0.5 nm of an average length for all conducting slabs prior tothe operation of gas-phase etching the electrically-shorted conductingslabs.
 14. The method of claim 12 wherein each conducting slab ischaracterized by a length parallel to the substrate, and wherein thelength of each slab is within 0.5 nm of an average length for allconducting slabs after the operation of gas-phase etching theelectrically-shorted conducting slabs.
 15. A method of etching apatterned substrate, the method comprising: placing the patternedsubstrate in a substrate processing region of a substrate processingchamber, wherein the patterned substrate comprises electrically-shortedtungsten slabs arranged in at least one of two adjacent verticalcolumns, wherein a trench is disposed between the two adjacent verticalcolumns, wherein the tungsten slabs are disposed vertically from oneanother within the vertical columns, and wherein each tungsten slab isvertically separated from at least one other tungsten slab by a regionof silicon oxide; flowing a radical-fluorine precursor into thesubstrate processing region; and selectively etching theelectrically-shorted tungsten slabs, wherein selectively etching theelectrically-shorted tungsten slabs electrically isolates each of theelectrically-shorted tungsten slabs from one another to formelectrically-isolated tungsten slabs.
 16. The method of claim 15,wherein the tungsten slabs are electrically shorted by a region oftungsten extending perpendicular to the substrate and contacting eachvertically separated tungsten slab.
 17. The method of claim 16, whereinthe selective etching removes the region of tungsten extendingperpendicular to the substrate.